Process for separating wax from oil



Filed Aug. 22, ,1935

Patented Nov. i7, i942 V2,302,177 PROCESS FORl SEPARATING WAX' FROM OILUlric` B. Bray, Palos Verdes, and VClaude`E. Swift, Glendale, Calif.,assignorsto `Union OilA Com-` v pany ofA California, Los Angeles,Calif., a corporation of California Y Application August 22,1933,-Serial No. 686,552,754V

f folaims. (o1. 19a-18)` line, gas oi1, ory heavy lubricating oilfractions i This invention relates toa process'for. the separation ofwax from oil and is a. -continuation in part of Serial No. 555,018,filed 'by Ulric B. Bray and Claude E. Swift on August 4, 1931.

The invention relates primarily to a process for' the separation of waxfrom oil bythe use of materials which cause wax to be less soluble.L inoil fractions and which hereinafter will be referred to as waxanti-solvents.

In our prior application, referred to above, We disclosed a process fortreatingoils tojproduce lubricating oils which included the steps ofVdiluting the oil with aLdiluent preferablya liquid normally gaseoushydrocarbon such'as liquid 4propaneand then treating the diluted oilwith a selective solvent such as liquid `sulphur dioxide, acetone,mixtures of acetone and benzohaniline or methyl formate, for the purposeof-splitting the oil into a relatively parainic 'fraction or fraction ofhigh viscosity vindex and a relatively nonparainic fraction or afraction of low viscosity index. The fraction of relatively highviscosity index containing the @propane and a portion of the selectivesolvent Was then chilled to, say, approximately 40 F., preferably bypermitting a portion of the propane to vaporize under reduced pressurewhereupon wax precipitated from solution. The solution containingtheprecipitated wax was then lteredto remove the wax from the oil andsolvents.` The wax-free solution Was then chemically treated such aswith sulphuric acid and clay afterwhich the'remaining propane and liquidsulphur dioxide Was vaporized from the treated oil.

In the aforesaid process, we observed that the portion of selectivesolvent retained in the paraiinic fraction or raffinate phase materiallyaided inthe subsequent separationvof the wax from the oil. The presentcontinuationis basedupon the'foregoing observation and is directed toAnot only the dewaxing of a rainate produced by selective solventextraction but also the dewaxing of other waxy oils which have notpreviously been subjected to'actionof selective solvents Vby comminglingthe waxy oil with a diluent and a small amount of selective solventsprior to chilling. Furthermore, the selective solvent otherwise known asa wax anti-solvent may not only be `added to the oil and diluent priorto chilling` but may also be introduced into the diluent oil solutionduring or upon completion. of the' chilling operation.

This invention contemplatesthe use of `not only normally gaseoushydrocarbon diluents such .as

propane, but also such diluents as kerosene, gaso- 55 whichare-substantially wax-free.

vIn vcarrying out the invent'on the wax ycontaining fraction isdissolved in -onevof the foregoing diluents. A small quantity of one oftheforegoing selective solvents is then added and the mixture isthencooled to a temperature sufficiently lowto precipitate the Wax. Thesolutioncontaining the precipitated wax isv then filtered, cernltrifuged or settled to separate the wax from the oil. The de-waxed oilcontaining the-diluentand the waxV anti-solventV is then distilled toremove the diluentand anti-solvent from thede-waxed oil. Y Y Y "Inj,carrying out the process-1` as described.k above the solution of waxyoil diluent and anti-solvent may be chilled-by circulating cold brine inindirect heat `exchange with the solutionil to-be chilled or byinjecting liquid ammonia,A liquid sulphur dioxide, liquid carbondioxide, or other liquid materials which are normallyg-aseous underordinary temperatures and pressures into the solution, and allowingthese materials to vaporize at a reduced'pressure therebychilling theAoil and precipitating the-wax. f A

Another -meansvof chilling consists in addingto the oilnormallygaseoushydrocarbons such as liquid propane, liquid ethane, liquid butanepliquidpropylene,v -liquidbutylena and other normallygaseoushydrocarbons alonglwith. thek wax anti-solvent, vand thenvallowing a portion: ofv thenormally gaseous hydrocarbon to vaporize under reduced pressure, therebychil-ling the oil and precipitaktingv the Wax. rI *he chilled lmass.istreated in the same Vmanner as described.y above .for the separationof the wax from the oil.

It is therefore an object of this invention to add anti-solvents towaxy-oils to-aid in the separation of the wax-from the oil.

It is a further object of this invention to dilute waxymoils withsuitable diluents such as liquid propane. gasolinarkerosene or sas 011,Yadd antisolventsl to 'this solutionvof-.waxy oil andl then separate vthewaxfrorn the' yoil'. Y

.It isla further object' of this invention to; dilute waxy loils vwithliquid propane, .addanti-solvents selected from the class of sulphurdioxide,ani line, chloranilina nitrobenzol, dichlorethylether, acetoneand benzol or methyl-formate, cool the solution to a temperaturesufliciently low to precipitate the wax, and then separate theprecipitated wax from Athe propane solution of'oil and anti-solvent.

In carrying out our process a waxy oil isgdiluted with from l to 3volumes of liquid propane ata Uff! temperature of about 70 F. and undersuilicient pressure to maintain the propane in the form of a liquid. Thepropane solution of oil is then mixed with from 10 to 25% of sulphurdioxide by volume and the mass is then cooled either by vaporizingpropane under reduced pressure or by any suitable indirect refrigerationmeans to a temperature sufficiently low to precipitate the wax. Thetemperature of the chilled mass will vary. However, in most cases wefind that temperatures ranging from 0 F. to minus 20 F. are sufficientlylow to precipitate a substantial portion of the wax present in solution.The chilled mass containing precipitated wax is then settled,centrifuged or filtered for the separation of the precipitated wax fromthe propane solution of oil and sulphur dioxide. The dewaxed oilcontaining propane and sulphur dioxide is then distilled to separate thepropane and sulphur dioxide from the oil.

In some cases more sulphur dioxide or other anti-solvent is added to theoil than remains in the solution at the lowered temperature. In thesecases the excess is allowed to settle out and is removed at the end ofthe chilling step from the chilled mass prior to the separation of theprecipitated wax. This is accomplished by allowing the chilled mass tosettle for a short time in a quiescent state. As the chilled masssettles in a quiescent state anti-solvents which we have describedsettle to the bottom of the vessel owing to their relatively high specicgravity. These anti-solvents may then be withdrawn from the bottom ofthe vessel away from the chilled mass.

The chilled mass from which the excess anti-solvent has been removed maythen be passed to wax separation means for the separation of theprecipitated wax from the propanesolution of oil and anti-solvent.

A number of methods may be employed for the addition of the antisolventto the oil to be dewaxed. For example, the diluent such as liquidpropane, kerosene, gasoline or gas oil may be saturated with theantisolvent such as liquid sulphur dioxide at an ordinary temperature.VYThe diluent saturated with antisolvent may then be mixed with a waxyoil. Usually this mixing is carried out at a temperature and underconditions which will render the waxy oil soluble in the diluentcontaining the antisolvent. This solution is then chilled to atemperature sufficiently low to precipitate the wax. The chilled massmay then be passed to any suitable wax separation means such as thellter press, settling chamber or centrifuge for the separation of thepre- ,I

cipitated wax from the chilled mass. The dewaxed oil recovered from thewax separation means may then be distilled in order to separate thediluent and antisolvent from the dewaxed oil.

If desired, the waxy oil may be saturated with an antisolvent such assulphur dioxide diluted with a suitable diluent as described above,chilled to a temperature suiiciently low to precipitate the wax and thechilled mass may then be filtered, centrifuged or settled to separatethe precipitated wax from the mass.

As a further modification of this process a waxy oil may be diluted witha suitable diluent such as liquid propane, gasoline, naphtha, keroseneor gas oil and chilled to a temperature sufciently low to precipitatethe wax. The precipitated wax may then be separated from the mass andthen a portion of one of the foregoing antisolvents may be injected intothe chilled mass for 75 the precipitation of a further quantity of waxwhich may be separated from the diluted oil by any one of the foregoingmeans.

As a further modification we may inject any one of the antisolventswhich we have described continuously during the chilling step or ifdesired it may be injected after the chilling step and then theprecipitated wax may then be separated from the diluents and oil.

It is therefore an object of the present invention to injectantisolvents, selected from the class of aniline, cresylic acid, phenol,chloraniline, sulphur dioxide, nitrobenzol, dichlorethylether, acetoneand benzol, and methyl formate into a waxy oil dissolved in a diluentduring the chilling step Vto aid in the separation of the wax from theoil.

It is a further object of the present invention to mix antisolvents withchilled waxy oil and diluent to aid in the separation of the wax fromthe oil.

It is still'a further object of the present invention to dissolve waxyoil in a diluent, chill the mass to a temperature suiciently low toprecipitate wax, separate the precipitated wax from the oil, mix thechilled mass from which the precipitated wax has been separated with anantisolvent such as sulphur dioxide, aniline, phenol, chloraniline,nitrobenzol, dichlorethylether, cresylic acid, acetone and benzol or'methyl-formate and separate a further quantity of Wax withor Withoutfurther cooling.

It is still a further object of the present invention to mix a waxy oilwith a diluent, chill the dilutedwa-xy oil and then mix the chilled oilwith an antisolvent such as sulphurv dioxide, phenol, chloraniline,nitrobenzoL clichlorethyletherycresylic acid, methyl-formate, aniline oracetone and benzol 'to aid in the precipitation 'of wax from the dilutedoil. f

It is only necessaryV to employ suflicient of the foregoing waxantisolvents to saturate the oil at the temperature at which the wax isremoved. Any excess of these antisolvents which would tend to produce anoil phase saturated with these wax antisolvents and a phase consistingof Vantisolvent containing some dissolved oilfractions should beavoided. Where phase separation occurs due to too large an excess of the'antisolvent some of the wax fractions may be dissolved in theantisolvent phase containing dissolved oil fractions and thus not beprecipitated and removed from the oil during Vthe wax separation step.

Our process may be more easily understood by referring to the ligure.Referring more specilically to the figure a waxy oil in tank I, at atemperature above its congealing point is withdrawn through line 2,valve 3 and line 4 to pump 5 which forces it throughline 6 where itmeets a stream of diluent coming from tank 8 through valve 9, line I0,pump II, line I2, mixing coil IS-and'line I 4. The mixture of waxy oiland diluent in line 6 passes into mixing coil 1 where'it is thoroughlyagitated. The agitation here in most instances is sufficient to produce`a solution of the waxy oil in the diluent. The solution of the waxy oilin the diluent may be facilitated if desired in agitating coil 'I byraising the temperature of the diluent in waxy oil by some means notshown. The solution of a waxy oil in the diluent emerges from agitatingcoil 1 to line I5 where it'is mixed with antisolvent withdrawn from tankI8 through pump I9, line 20, valve 2 I, l The antisolvent passes intoline I5 alongwith theoil and diluent from whence it passesinto mixingcoil 54` where the 'mass is thoroughly mixed. From mixing'coil54 themass passes into Chiller I1 Where the teinperature of the mass 'islowered sufficiently to cause a precipitation of the wax. Where heavydiluents such as naphtha, gasoline, kerosene or gas oil are employedexternal refrigeration must be supplied to the mixture of diluent oiland antisolvent in chiller I1 in order to attainatemperature suicientlylow to precipitate the wax.

Where a normally gaseous liquefied hydrocarbon such as liquid propane isemployed as the diluent in Chiller II the refrigerationfmay be obtainedby opening valve 28 and allowing afpertion of the diluent tovaporizeunder a vreduced pressure. The vaporized 'diluent'being releasedthrough valve 28 passes through line 29, pump 33, line 3I, pump 46,line-41, condenser 43 and line 49 to receiving tank 5I). v

In Case more antisolvent has been injected into the mass in Chiller I1than remains soluble at the lower temperature, this excess ofantisolvent can be settled out by maintaining the mass in Chiller I1 ina placid state. The antisolvent collects in the bottom of chiller I1 andis removed by pump 32, line 33, valve 34 and line 35 from the system.

The chilled mass in Chiller I1 is then removed through valve 32, line33, valve 35 and line 31 to wax separation means 38 where the wax isseparated and removed to line 33. dissolved in solvent is removedthrough line 4I), pump 4I and valve 42 to heater 43. Heat is supplied tothe mass in heater 43 by coil 55 through which steam or other heatingmedium is supplied.

The diluent and antisolvent are vaporized in heater 43 and passedthrough line 44, valve 45, pump 46 and line 41 to condenser 48 wherethey are condensed. The liquefied diluent and antisolvent pass fromcondenser 43 through line 43 into collecting chamber I).

The liquid collected in chamber 53 Consists of recovered diluent andantisolvent. This material may be returned to the cycle through line I2.If desired, a further quantity of antisolvent may be injected into theliquid passing from line 53 into line I2 by opening valve 23 and forcingantisolvent through pump I3, line 23, line 22, valve 23 and line 24 intoline I2. This mixture of material passing through line I2 from line 53and antisolvent passing into line I2 from line 24 passes into agitatorI3 where the two materials are thoroughly mixed before introduction ofthese materials into the stream oi" waxy oil withdrawn from tank I intoline 6.

The antisolvent in tank I8 may also be employed to saturate the diluentin tank 8 by mixing the fresh diluent withdrawn from tank 8 into line I2with antisolvent withdrawn from tank I8 through line 24. Fresh diluentin tank I2 and the antisolvent Withdrawn through line 24 are mixed incoil I3 and pass through line I4 into line 6 where the diluentcontaining the antisolvent is mixed with fresh waxy oil withdrawn fromtank I into line 6.

If desired, the antisolvent may be injected into the oil diluent incooler I1 during the chilling step. In this case the oil in tank I andthe diluent in tank 8 are withdrawn as previously described into mixingcoil 1 and then pass into Chiller I1. As the refrigeration is suppliedto the material in chiller I1 by external means or by vaporizing aportion of the diluent, as previously described, antisolvent in tank I8is introduced into Chiller I1 through pump I9, line 20, line 22, valveand line 26.

The dewaxed oil lAs a Yfurther modication. -the vmixturelof .oil

-and diluent in' chilling chamber f I 1 'canbe comand then we may addtheL antipletely chilled from tank I8 by solvent into vchilling tank I1the-method just described.

As We'have already stated-we may also remove the Wax from the oil insteps. In the first step we may not use antisolvent. In this case theoil in tank I and the diluent in tank 8 are mixed in coil 1 and arepassed into Chilling Chamber I1. The waxyoil and diluent in chiller I1are then Cooled'by external refrigeration or if the diluent is normallygaseous a portion of this material may be vaporized under reducedpressure until a temperature .is obtained'in chiller I1 at which aportion of the-wax is precipitated. The

chilled mass in tank I1 is then 'removed through pump,32, line 33,valve'3'6,"line 31 to wax separation means-38vvher'ethe waxis separatedfrom the oil and removedthrough line 39. The de- Waxed oil 'recovered inline 540 may'then be returned tov Chiller I1'by means not shown in thisdrawing, andladmixed with antisolvent frcmtank I8 through pump I9, line23, line 22, valve 25 and line 26.

In some cases it may be necessary to further chill the oil in chiller I1to obtain any substantial separation of Wax, and in some cases the coldmaterial passing from the wax separation means 38 back to Chiller I1 issuiciently cold to obviate the necessity of further refrigeration forthe separation of the further quantity of wax provided antisolvents areinjected or mixed with this cool material. The cooled mass in chiller I1is again withdrawn through pump 32, line 33, valve 36 and line 31 to waxseparation means 38 where the precipitated wax is sep-1 arated from thediluent oil and antisolvent.

In some cases it may be found necessary to acid-treat the oil prior tothe separation of the wax with diluents and antisolvents. In this casethe oil in tank I may be an oil which has been previously contacted withsulphurc acid for the separation of materials which hinder theseparation of wax from oil.

We have used the term propane in this speciiication to include membersof the normally gaseous hydrocarbons such as ethane, propane, butane andmixtures thereof. It is to be understood, however, that other normallygaseous hydrocarbons may be employed in our process to advantage-forexample- We may employ liquid ethylene, propylene or butylene ormixtures thereof, or we may employ hydrocarbons which are normallygaseous and which are halogenated--for example-We may employ methylchloride, ethyl chloride or dichlore-difluor-methane. We may also employas diluents normally gaseous ethers or normally gaseoushalogenatedethers or mixtures thereof.

As a specic example of the method of carrying out our process a Santa FeSprings distillate having a specific gravity of 32.8 A. P. I. and a pourpoint of F. was mixed with liquid propane and liquid sulphur dioxide inthe following proportions:

Volume Liquid propane 4 Liquid sulphur dioxide 1 The Santa Fe Springswaxy oil l This mixture was then agitated and cooled by external meansat the rate of 1.2 F. per minute until a iinal temperature of 15 F. wasobtained. The chilled mass Was then filtered to separate theprecipitated wax from the oil, propane and sulphur dioxide. The ltrateconsisting of dewaxed oil, propane and sulphur dioxide was thendistilled to remove the propane and sulphur dioxide from the dewaxedoil. 'I'he oil dewaxed by the foregoing method had a pour point of 5 F.

It is to be understood that the foregoing examples are merelyillustrative of our process and are not to be construed as limiting theinvention which we claim.

We claim:

l. A process for the separation of Wax from oil comprising mixing saidoil with liquid propane, vaporizing liquid propane under reducedpressureto chill the oil, adding a Wax antisolvent and separating Waxand subsequently separating the separated wax from the oil, remainingliquid propane and wax antisolvent.

2. A process as in claim 1 in which the Wax antisolvent is liquidsulphur dioxide.

3. A process as in claim 1 in which the wax antisolvent is added duringthe chilling step.

4. A process as in claim 1 in which the wax antisolvent is liquidsulphur dioxide and said liquid sulphur dioxide is added during thechilling step. Y u

5. A process for the separation of wax from oil comprising mixing theoil with a liquid normally gaseous hydrocarbon diluent, chilling saiddiluted oil to precipitate the Wax by vaporizing a portion of thediluent under reduced pressure, adding a wax anti-solvent to the chilledsolution containing the precipitated wax and subsequently separating theprecipitated wax from the oil, diluent and wax anti-solvent.

6. A process for the separation of wax from oil comprising mixing saidoil with liquid propane under superatmospheric pressure, chilling thesolution of oil and propane to precipitate wax by reducing the pressureto vaporize a portion of the propane, adding liquid sulfur dioxide tothe chilled solution containing the precipitated wax and subsequentlyseparating the precipitated Wax from the oil, propane and sulfurdioxide.

ULRIC B. BRAY. CLAUDE E. SWIFT.

